Holding(s) in Company

TR-1: NOTIFICATION OF MAJOR INTEREST IN SHARES

1. Identity of the issuer or the underlying issuer of existing shares to which voting rights are attached:

ARM HOLDINGS PLC

2 Reason for the notification (please tick the appropriate box or boxes):

An acquisition or disposal of voting rights

YES

An acquisition or disposal of financial instruments which may result in the acquisition of shares already issued to which voting rights are attached

NO

An event changing the breakdown of voting rights

NO

Other (please specify):

N/A

3. Full name of person(s) subject to the notification obligation:

JANUS CAPITAL MANAGEMENT LLC

4. Full name of shareholder(s) (if different from 3.):

5. Date of the transaction and date on which the threshold is crossed or reached:

23 SEPTEMBER 2010

6. Date on which issuer notified:

24 SEPTEMBER 2010

7. Threshold(s) that is/are crossed or reached:

11%

8. Notified details:

A: Voting rights attached to shares

Class/type of shares

if possible using the ISIN CODE

Situation previous to the triggering transaction

Resulting situation after the triggering transaction

Number of Shares

Number of Voting Rights

Number of shares

Number of voting rights

% of voting rights

Direct

Indirect

Direct

Indirect

143,311,803

143,311,803

141,954,072

141,954,072

10.76%

GB0000595859

B: Qualifying Financial Instruments

Resulting situation after the triggering transaction

Type of financial instrument

Expiration date

Exercise/ Conversion Period

Number of voting rights that may be acquired if the instrument is exercised/ converted.

% of voting rights

C: Financial Instruments with similar economic effect to Qualifying Financial Instruments

Resulting situation after the triggering transaction

Type of financial instrument

Exercise price

Expiration date

Exercise/ Conversion period

Number of voting rights instrument refers to

% of voting rights

Nominal

Delta

Total (A+B+C)

Number of voting rights

Percentage of voting rights

141,954,072

10.76%

9. Chain of controlled undertakings through which the voting rights and/or the financial instruments are effectively held, if applicable:

Proxy Voting:

10. Name of the proxy holder:

JANUS CAPITAL MANAGEMENT LLC

11. Number of voting rights proxy holder will cease to hold:

1,357,731

12. Date on which proxy holder will cease to hold voting rights:

9/22/2010

13. Additional information:

14. Contact name:

JOANNE O'SULLIVAN

15. Contact telephone number:

0044 1223 406122